Not at all familiar with Toyota, so this may be completely different. Is the wire actually connected under the hood at the fuse box? I know with most GM products, the wiring is there but has to be connected in order to get power back to the trailer harness. In my case there are two terminals located by the fuses for the brakes and 12V battery connection. I had to find the wires under the hood and connect them. This may have already been done, or may not be necessary, just throwing out ideas.
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